This invention relates generally to inspection of parts, and more particularly to the detection of anomalies in finished manufactured parts.
During the manufacturing of complex 3D structures, there is a possibility of foreign material occurring in internal passages or cavities. For example, in the machining of complex parts or assemblies with inner passages, machine chips may lodge inside. If the passages do not easily allow either visual or mechanical access, it may be difficult to be absolutely sure no chips remain inside.
In the manufacture of turbine blades for aircraft, a ceramic core is often used to form complex inner cooling air passages. To check whether the ceramic core has been removed by a subsequent chemical cleaning, the blades are often sent for neutron radiography, which results in the loss of considerable time in the manufacturing and approval process. Parts are often laser drilled or EDM (electron discharge machining) drilled to form cooling holes. Sometimes these holes converge, and it may be difficult to detect the exact point of convergence. In addition, pipes and parts may suffer corrosion or erosion in use, and it is not easy to determine how much good material remains.
Non-destructive examination of parts can be performed by one or more known techniques, which include, for example, radiography, ultrasonics, and acoustic emission. For the most exact location of problems inside parts it has been found that computed tomography showing cross sections is most helpful.